Box already has close ties with Windows and Windows Phone developers, and now they're getting tighter.

At Build, Box revealed that it's working with Microsoft on a couple of new fronts:

Box is now integrated with Windows Azure Active Directory (AD), Microsoft's cloud based admin tool for managing identities and access to apps. This means enterprises can work with Box accounts from within Microsoft's Windows Azure cloud.

"Any enterprise using Active Directory can easily set up and manage Box accounts for their users within their existing identity management system," Simon Tan, Box's product manager of Mobile, said in a Thursday blog post.

Box also launched a new software tool for Windows developers, which lets them build Windows and Windows 8 apps that use Box, Tan said. Box already offers similar tools for iOS and Android.

Box's competition with Microsoft's SharePoint file-sharing and collaboration is pretty intense. But judging from Levie's Build appearance, he's happy with how the Windows partnership is going.